1920] A Little Known Vetch Disease 79 



i 



leading to a brown ovoid appresorium and penetration will have been 

 accomplished, Figs. 18, 19, and 20. The infection tube arises from 

 the lower side of the appresorium and effects entrance into the epi- 

 dermis by dissolution of the cell wall. This process was observed 

 several times in 1919 and confirmed during the present season. The 

 mycelium then grows rapidly into adjacent cells and forms a new 

 acervulus at the locus of infection. Within three to four days after 

 infection has occurred, new acervuli have matured and are shedding 

 their conidia, Fig. 21. 



Life History of the Causal Organism 



The false anthracnose fungus possesses only one type of repro- 

 ductive structure which in the vicinity of Raleigh, N. C, may be 

 produced at any time during the life of its host, or from early in 

 November until the first of July. The organism bearing mature acer- 

 vuli and conidia has been collected during each month of this eight- 

 month period. It is first evident upon the seedling plants and may 

 cause the outer cortical portions of the stems to be blackened to a 

 height of several inches above the surface of the ground, without, 

 however, invading the xylem portions. The disease makes little prog- 

 ress during wdnter, however, and only develops rapidly with the ad- 

 vent of favorable conditions which appear usually about the middle of 

 April. It then spreads upward and involves all of the above-ground 

 parts including the pods. Here it usually does not extend more 

 deeply than the skeletal or supportive tissue of the pod wall. Fig. 8, 

 but it may penetrate into the young seed. In case of severe infections 

 such as occurred in 1919, the seed are prevented from developing. Le- 

 sions on young seeds show as discolored areas which are not noticeable, 

 however, when the seed have matured. If mature seed taken from 

 directh' beneath lesions on the pod wall, are soaked in equal parts of 

 alcohol and glycerin for several months to permit them to soften, and 

 are sectioned, the hyphae or Protocoronospora will be found to have 

 permeated all parts of the seed. Such an infected seed is shown in 

 section in Fig. 12. The palisade-like cells of the young seed repre- 

 sented in Fig. 8-d, have become the Malphigian layer, Fig. 12-a, 

 whose outer cell walls are thickened and show a highly refractive 

 "light line."" Beneath is the scleroid la.yer subjacent to which is the 



' An illuminating account of the structure of legume seeds to which the reader is 

 referred was prepared by Pammel, L. H. Anatomical characters of the seeds of Legu- 

 minoseae, chiefly genera "of Grav's Manual. Trans. Acad. Sci. St. Louis. 9 ; No. 6, pp. 

 91-273, pis. 7-35. 1899. 



